The Chapman plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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3.89 inches of rain fell in two days, the most for this week of the year since records began in 1893. The next wettest, 2.87 inches, fell in 1935.
Chapman’s center stands about 700 ft above sea level. Within three miles the land runs from 380 ft to 830 ft, a difference of 450 ft: hilly country. The highest named summit within 15 miles is Broad Mountain, about 1,790 ft, 15 miles southeast.
Under the town center the state geologic map shows Irish Valley Member of Catskill Formation (siltstone), from the Late Devonian, 359 to 384 million years old.
The section below crosses 14 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 12×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Black-shale. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 4 mi of the line.
Siltstone. Age: Late Devonian, 359 to 384 million years old. About 4 mi of the line.
Shale, siltstone, sandstone. Age: Carboniferous, 324 to 359 million years old. About 3 mi of the line.
Siltstone, shale. Age: Late Devonian, 359 to 384 million years old. About 2 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Shale, sandstone. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 8 smaller units along the line are not listed.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Chapman reaches Chesapeake Bay and the Atlantic Ocean by way of Hoffer Creek and the Susquehanna: about 110 river miles.
Lake on the way: Lake Aldred.
65 miles of the trip are on the Susquehanna.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Chapman; river miles along the main stem, rounded.
Chapman has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 19° in January. A normal year brings about 29 inches of snow; with the rain, that comes to about 43 inches of water.
On November 14 Chapman normally reaches 52° and falls to 32°. The record high is 68°, in 1902; the record low 14°, in 1920. The most rain on this date, 0.69 in, fell in 1988.
Normals 1991–2020 and records since 1893 at Selinsgrove Penn Valley Airport, 10 miles north-northeast, 260 ft lower. NOAA, through RCC-ACIS.
